1. Field of the Invention
This disclosure is related to the field of metal cutting machines. More specifically, the present disclosure relates to systems, devices, methods and processes for cutting shapes into sheet metal for ductwork as part of a coil-line manufacturing system.
2. Description of the Related Art
Ductwork is a central component of forced-air heating and cooling systems. In building structures with forced-air heating and cooling systems, ducts are used to distribute air throughout the structure. Stated differently, air ducts are the throughways through which treated air from heating or conditioning equipment in forced-air systems is distributed throughout the building structure.
Air ductwork is usually constructed out of thin metal sheets. Galvanized mild steel is the standard and most common material used in fabricating ductwork. Generally, ductwork construction starts with cutting and forming these thin metal sheets into component subparts in a manufacturing facility, attaching an insulative material known to those of ordinary skill in the art to one side of the thin metal sheets (if the sheets are to be insulated), transporting the finished ductwork component parts to the building structure, and constructing the air ductwork throughways on-site at the building structure.
Currently, plasma cutting is one of the methodologies most commonly utilized to cut the thin metal sheets into the desired component parts when fabricating ductwork. Generally, plasma cutting is a process that is used to cut steel and other materials of different thickness with a plasma torch. In the plasma cutting process, an inert gas (such as compressed air) is blown at high speeds out of a nozzle. At the same time, an electric arc is formed through the gas from the nozzle to the cutting surface, turning some of that gas into plasma. Generally, the plasma is sufficiently hot to melt the metal being cut and moves sufficiently fast to blow molten metal away from the cut.
Generally, there are two main types of plasma cutting tools. As would be understood by those of ordinary skill in the art, an HF plasma cutting tool uses a high-frequency, high-voltage spark to ionize the air through the torch head and initiate an arc. Accordingly, the torch does not need to be in contact with the raw material to be cut when starting. The other type of plasma cutting machine, a pilot arc, uses a two cycle approach to producing plasma, also avoiding the need for initial contact. In the pilot arc machine, a high-voltage, low current circuit is used to initialize a very small high-intensity spark within the torch body, thereby generating a small pocket of plasma gas which is called the pilot arc. The pilot arc has a return path built into the torch head. The pilot arc will remain within itself until it ignites the main plasma arc.
In industrial cutting settings, a plasma cutter can be utilized by hand. However it is more common for the process to be automated. In both of these methodologies, a cutting table is utilized. The raw material to be cut with the plasma cutting machine—in the case of duct work, sheet metal—is placed onto a machine table, a large flat surface, and located to stops on the table and held in place. The table is generally sized to the size of the sheet metal used. The most ubiquitous plasma cutting methodology in the prior art are CNC cutting tables. In the CNC cutting table methodology, a computer controls the torch head, producing clean, sharp cuts in the desired programmed pattern.
Notably, during this entire process the sheet metal is held rigidly to the table and the material used is generally a sheet of confined size. Generally, the sheet metal is not manipulated in these prior art processes because it adds an additional degree of complexity to the cutting process. Instead, in these processes, the sheet metal is held stationary while the plasma cutter is manipulated on a carriage and gantry moveable in the X and Y axes. CNC plasma cutter and cutting tables have a wide use in the HVAC industry as the cutter of choice for the component parts of ductwork fittings (that is components that are not simply straight) such as offsets, elbows and transitions. Plasma cutters also are commonly used to form cutouts within other ductwork structures such as to allow for the connection of two ducts at angles and for input and output holes.
While the utilization of plasma cutters, and CNC plasma cutting methodologies in particular, has increased productivity in the HVAC industry since its introduction in the early 1980s, there are still numerous drawbacks with both this and the manual methodology. The first problem is a lack of precision and improper cuts. In the manual method, the reason for this lack of precision is simply basic human error. There also can be over or under correcting as a user of a plasma cutter manually attempts to follow a marked pattern. In the automated method when producing full length straight ducts, the ducts generally must be smaller than the sheet it is made from in order to allow for cutting and positioning of the cutter over the sheet. This produces a necessary amount of waste material. Additionally, the construction of the ductwork will require additional forming operations to be completed manually as the cutting process can generally only take place on sheet metal which is flat and has not been folded into the 3-dimensional duct shape.
Another problem with existing methodologies is cost. Specifically, in the manual method, the cost of the laborer who is manipulating the plasma cutter must be included in the overhead cost for the ductwork. The cost of the laborer must also be considered in the automated methods where an additional manual secondary operation step (such as final finishing of the ductwork) must be performed.
Another problem, closely related to cost, is time. The manual process, in addition to the cost of labor, is also time intensive. Moreover, the automated CNC plasma cutting process, while faster than the manual methodologies, is not sufficiently fast enough for many manufacturing facilities due, in part, to the additional final finishing steps which are performed manually and the need to transfer parts to and from the cutting table. Notably, even the most advanced currently utilized automated CNC plasma cutting methodologies are not fully automated. In many of these systems, a user is still required to manually locate positions required to complete the cutting.
In addition, neither of these methodologies is traditionally utilized in HVAC coil-lines. HVAC coil-lines are ubiquitous in the HVAC industry and, generally, offer a complete integration of processing metal for ductwork up to the point where connection accessories are utilized in the field to assemble the ductwork. Generally, coil-lines offer the fastest methodology for making straight ductwork, offer a more accurate ductwork manufacturing process, and reduce material waste and operating costs while producing a superior product. Coil-lines generally comprise a standard number of pieces for cutting, bending, transporting, and otherwise manipulating the coil of material which are tied together by a controller and conveyor belt or roller system for advancing the coil material through the coil line.
Generally, when making straight ductwork on a coil-line it is common for a manufacturer to maximize cost efficiency by utilizing a lighter gauge of metal to lower the cost of the material components of the ductwork. To compensate for the decrease in stability and strength associated with the lower gauge metal, a reinforcement system is generally used in ductwork to achieve the stability lost by utilizing the lighter gauge sheet metal.
One commonly used methodology for reinforcing ductwork is a tie rod-based system. Commonly, these tie rod-based systems require different sized holes in the ductwork for bolts, tie rods and dampers of varying sizes to be connected. In currently utilized coil-lines, the required holes for ductwork reinforcement systems are generally achieved through an automated punching methodology integrated into the coil-line. These are generally mechanical die punches which are simply dropped onto the coil material to form a hole corresponding to the size of the die head.
However, there are numerous problems with this methodology. First, the automated punching methodology is generally only able to punch a single-sized circular hole in the sheet metal with each die head. If a different sized hole is desired, the head of the automated punching system must be switched out. This requires a stoppage of the coil-line and a resulting loss in efficiency. To compensate for this inefficiency, one current general practice in the art is to simply punch holes that correspond to the largest required hole and compensate with washers or similar type of devices where required. Obviously, this arrangement is less than ideal and, at these points, creates possible areas of weakness or leakage in the ductwork.
Further, the automated punching methodology utilized in coil-line systems is generally unable to create holes of different shapes; e.g., square or triangular holes, or particularly large holes such as can be necessary for interconnecting duct pieces with each other. Instead, if these holes are desired, they currently have to be created in a secondary post coil-line step manually or through using a plasma cutting table methodology such as those described previously. This has obvious negative ramifications on efficiency.
In addition, it is often common to place accessory holes or openings (e.g., an access door) or openings for branches and sub-branches in ductwork. Generally, this is accomplished by cutting holes in the ductwork for the door, branch or sub-branch. As this is often performed after the duct is assembled, this step often requires manual cutting and all the attendant problems and inefficiencies.
Currently, cutting of internal structures such as large holes or cut-outs is not a step that can be achieved in the coil-line process. Further, generally odd shapes which may require curved cuts or cuts at uncommon angles can generally not be performed in the coil line as the mechanical punches and guillotine cutters which are particularly useful for performing a large number of repeated cutting operations are unable to make any form of unique or specialized cut. Accordingly, it is generally performed in a secondary manual step in the shop or in the field utilizing a plasma cutting machine or metal cutting scissors.
These later cutting stages can be restricted by the size of the table for the plasma cutter, as would be understood by those of ordinary skill in the art, limiting the shapes of ductwork which may be created. Again, this secondary step also increases the cost, labor and complexity associated with manufacturing ductwork.
While straight line ductwork can be manufactured on an automated plasma cutting machine without the use of a coil-line and this methodology provides a mechanism in which holes and openings can be created in the ductwork, as noted previously, this method of manufacturing has numerous inefficiencies. For example, this process generally only produces a blank without end treatments which can be mechanically generated quickly and efficiently in coil line operations. Further, the finished ductwork product is formed in a batch as opposed to continuous process. Thus, all the additional work that can be automated on a coil-line machine (e.g., forming and bending, notching and shearing) must be done manually in a post-cutting step in the shop or in the field. Further, as the table requires a precut sheet with both dimensions dictated by the size of the table, certain shapes and cut components may be impossible, complicated, or particularly wasteful of material to form. Accordingly, there is a need in the art for a system and device for cutting a variety of shapes in the sheet metal that can be integrated into a coil-line.